Portable antenna having a mast formed of coaxial waveguide sections

ABSTRACT

A manually transportable HF radio antenna including a segmented mast which is easily assembled and disassembled and further functions as a low-loss feedline between radio and dipole radiating elements. A pair of dipoles are provided which allow a low standing wave ratio and also function as guy wire supports for the mast. Rigid dipole elements may be provided which switchably allow either a horizontally polarized mode or a vertically polarized mode of wave propagation.

United States Patent Inventors Richard C. F enwick;

Don L. Holzschuh; Betty M. Wicker, Richardson, Tex.; Paul B. Smithey, Sidney, Ill.

Oct. 1, 1968 Mar. 9, 1971 Collins Radio Company Dallas, Tex.

Appl. No. Filed Patented Assignee PORTABLE ANTENNA HAVING A MAST FORMED OF COAXIAL WAVEGUIDE SECTIONS 7 Claims, 9 Drawing Figs.

1.1.8. Cl 343/724, 343/797, 343/876, 343/884, 343/899 llnt.Cl H011; 1/00, HO lq 1/22 Field of Search 343/799, 820, 821, 822, 879, 880, 884, 890, 724, 797, 876, 899; 333/96 5 6] References Cited UNITED STATES PATENTS 1,933,941 11/1933 Taylor 343/222 2,643,334 6/1953 Aram 343/884 2,702,345 2/1955 Walter 343/823 3,189,906 6/1965 Kulik et a1. 343/890 2,200,338 7/1970 Mason 343/891 FOREIGN PATENTS 27,175 11/1913 Great Britain 343/846 Primary Examiner-Eli Lieberman Attorneys-Henry K. Woodward and Robert J. Crawford ABSTRACT: A manually transportable HF radio antenna including a segmented mast which is easily assembled and disassembled and further functions as a low-loss feedline between radio and dipole radiating elements. A pair of dipoles are provided which allow a low standing wave ratio and also function as guy wire supports for the mast. Rigid dipole elements may be provided which switchably allow either a horizontally polarized mode or a vertically polarized mode of wave propagation.

PATENTEUHAR 9|97l 3,569,970

sum 1 UF 6' INVENTORS. RICHARD C. FENWICK DON L. HOLZSCHUH PAUL B. SMITHEY BETTY M. WICKER BY 21 Z /WM A TORNEY PATENIEDMAR 9|97l 3569-970 sum 2 OF 6 FIG.2

INVENTORS. RICHARD C. FENWICK DON L. HOLZSCHUH PAUL B. SMITHEY BETTY M. WICKER A TORNEY PATENIEUIIAR 9|97l 3569870 SHEET 3 OF 6 IOO II TYPICAL INPUT RESISTANCE OF HALFWAVE DIPOLE OVER GROUND 2 80 I o f 2 TOTAL INPUT RESISTANCE a: 2 5 FIG. 40 Q I- y DIPOLE MODE 20 A RESISTANCE O 0.02 0.04 0.06 0.08 O.|O IO DIPOLE HEIGHT IN WAVELENGTHS 9 m POWER LOST TO BEVERAGE Q 8 MODE IN DIPOLE OVER GROUND Z 7 S E m 6 I FIG.4b 3 5 LU 5 m 4 o 3 35 3 I o. o

0 0.02 Q04 0.06 I 0.08 O.I0

DIPOLE HEIGHT IN WAVELENGTHS INVENTORS.

RICHARD C. FENWICK DON L. HOLZSCHUH PAUL B. SMITHEY BETTY M. WICKER ATTORNEY PATENTED MAR 9 I971 3569.970

saw u or 6 FIG.5

INVENTORS. RICHARD C. FENWICK DON L. HOLZSCHUH PAUL B. SMITHEY BETTY M. WICKER TORNEY PATENTEDMAR 915m SHEET 5 OF 6 INVENTORS.

m nm mwm BM H LS WM 0 0 HB R Y T LLTy M UT CNAE PATENIEUMAR 9m Mn 6 F 6 3569-870 DIPOLE INPUT FlG.7b

MONOPOLE MODE F/ 'NPUT INVENTORS. RICHARD C. FENWICK DON L. HOLZSCHUH PAUL B. SMITHEY BETTY M. WICKER BY 2/ MM! AT ORNEY PGIRTABLIE ANTENNA HAVING A MAST FORMED GIF CGAXIAL WAVEGUIDE SECTIONS This invention relates in general to radio wave propagating antennas, and in particular to an antenna which is easily assembled, disassembled, and transported and is also operationally effective in adverse topographical environments.

The conventional manually transported or manpack" high frequency radio utilizes a vertical whip antenna of up to about feet in length. With these antennas, communications are achieved on very short ranges by ground wave or surface-wave propagation, and longer paths are achieved by sky wave propagation where the propagated wave is bounced off ionospheric layers. An inherent characteristic of radio wave propagation using whip antennas is a zone of silence (skip zone) between the point where the ground wave signal becomes unusable and where the sky wave signal starts to become usable. (For further information on ionospheric propagation, see Radio Amateurs Handbook, American Radio Relay League, 45th Ed. 1968, pp. 380-383, for example).

The size of the skip zone is dependent on terrain and ground conductivity among other factors. Unfortunately, short range radio communication in a jungle or mountainous environment is severely limited because of attenuation of the vertically polarized ground wave from the antenna.

In such an environment, a much more effective mode of radio communication is by the sky wave propagation, i.e. bouncing radio waves from the transmitter off ionospheric layers to the receiving station. To achieve short range sky wave propagation horizontally polarized antennas, as opposed to vertical antennas, are required. Unfortunately, conventional design requirements for such antennas are not compatible with a manpack radio in terms of weight and ease of assembly. For example, for radio wave propagation in the high frequency range, a typical horizontally polarized antenna is supported horizontally between two support towers about feet above ground level. Such a design does not lend itself to ease of assembly, disassembly and manual portability.

An object of this invention is an improved transportable, horizontally polarized antenna.

Another object of the invention is a horizontally polarized antenna which is easily assembled, disassembled, and transported manually.

Still another object of the invention is a portable antenna structure which maybe polarized either horizontally or vertically.

Yet another object of the invention is a portable antenna that propagates radio waves simultaneously via ground wave and sky wave.

These and other objects and features of the invention will be apparent from the following description and appended claims.

Briefly, the present antenna is designed to be horizontally polarized and also permit physical mobility. Mobility is achieved through weight minimization, which in turn is achieved by positioning the antenna a minimum height above ground which will still allow effective radio communication. Minimization of antenna height is accomplished through a combination of factors including using a single support mast for the antenna and using a low-loss feedline between transceiver and antenna which is constructed to function as the support mast for the dipole elements of the antenna. Advantageously, the dipole element may slope from the mast and function as guy wire mast support. In one embodiment, switch means is provided to allow either a horizontally polarized mode or vertically polarized mode of wave propagation.

The invention will be more fully understood from the following description and appended claims when taken with the drawing in which:

FIG. I is a perspective view of an assembled antenna in accordance with the invention;

FIG. 2 illustrates the location of the radiating elements of the antenna of FIG. 1;

FIG. 3 is a perspective view of portions of the antenna support mast and coaxial feed cable of FIG. ll;

FIGS. 4a and 4b are graphs illustrating electrical characteristics of the dipole antenna above ground;

FIG. 5 is a perspective view of another embodiment of an assembled antenna in accordance with the invention;

FIG. 6 is a perspective view of the antenna of FIG. 5 illustrating the process of placing the antenna in an operating position; and

FIGS. 7a and 7b are schematic representations of the antenna of FIG. 4 illustrating different modes of operation.

Referring now to the drawing, and in particular to FIG. I, a perspective view of an assembled antenna in accordance with the invention is illustrated. The support mast It) comprises a plurality of segments 12 which fasten together (as further illustrated below with respect to FIG. 3) to function as a coaxial feedline between a transceiver 1 3 and dipole radiation elements I6, 17, 18 and 19 which are physically and electrically connected to the topmost segment of the mast Ill]. Each of the radiator elements terminate in a section of light rope 20 which is attached to a ground stake. The radiator elements along with the rope 20 function as guy wires for supporting the mast 10.

In its transport condition, the antenna may be packed in a canvas type package 22 which is carried on the shoulder or by hand. In one embodiment utilizing a 12 foot antenna mast, the package measures approximately 6 inches in diameter by 27 inches long and weighs-less than 14 pounds. When assembling the antenna, the bottom section of the antenna is mounted to a base plate or plugged directly to an antenna terminal of a radio (such as the military AN/PRC-47 field radio). The four radiator elements which are permanently fastened to the top section are stretched out and fastened to ground stakes. The remaining mast sections are then assembled and connected to the top mast section and base section. The final step in the installation procedure is adjusting the position of each ground stake, if necessary to plumb the mast. The entire assembly operation can be performed by one man in about l0 minutes.

FIG. 2 is a representation of the location of the radiating elements of the antenna. While a single dipole element may be utilized, the illustrated orthogonally mounted dipole antennas offer important advantages. Elements I6 and 17 form a long dipole and elements 13 and 19 form a short dipole, with the elements 16 and I9 grounded (connected to the outer conductor of the coaxial feedline 1-0) and elements 1% and 19 connected to the hot inner conductor of the coaxial feedline It). Advantageously, the dual dipole arrangement allows a lower standing wave ratio thus permitting lower transmission line loss. Further, the dipole arrangement also functions as the guy wire support structure.

There are two generic types of loss associated with antennas; namely, those associated with the transmission of energy to the radio antenna, and those associated with radiation of energy. Loss in the feedline system consists of the line attenuation plus any loss due to the presence ofstanding waves. These losses have been minimized by use of a low-loss transmission line and by matching the antenna to the field radio by suitable coupling means. An important factor contributing to the minimization of the antenna height in the present antenna is the provision of a low-loss coaxial transmission line from the radio to the radiating elements. This is accomplished in the present antenna by utilizing the mast as the coaxial feedline. Referring to FIG. 3, it is seen that each mast section is provided with an inner conductor male connector 24 which mates with a female connector 26 on an adjoining mast section. The inner conductor which is joined by the male and female connectors are positioned within the outer mast shell 28 and insulated therefrom by a dielectric material 30 such as polyurethane. The outer mast shell 28 is preferably made of aluminum or other lightweight metal and functions as the outer conductor of the coaxial feedline. The several mast sections slideably engage one another in assembling the mast.

Consider now the energy loss associated with the radiation of energy from the antenna. The efficiency of radiation associated with a horizontal radiator is a function of its height above ground, which in turn is dependent on the radio operating frequency range. When the radiator is close to the ground, energy is radiated in two modes. The sky wave dipole mode produces maximum radiation in the vertical direction, while the ground wave Beverage mode creates a vertical electrical field between the conductor and ground, producing a vertically polarized ground wave with a maximum radiation in the direction off the dipole or wire ends. For a fixed height above ground, the amount of the input power radiated proportionately in each of these modes is a function of antenna electrical length and the relative percentage of the antenna input resistance characterizing each mode. Each of these, in turn, is a function of the height above ground. The apparent antenna electrical length increases with decreasing height above ground, which reduces the efficiency of the dipole mode (rela tive to the total power input). The resistance of the Beverage mode increases with decreasing height and eventually becomes greater than that of the dipole mode. This effect of the antenna input resistance with height above ground is illustrated in FIGS. 4a and 4b. Of particular interest is the range of resistance with height occurring near the minimum of the total input resistance curve of FIG. 4a. If the horizontal dipole ofinterest is at a height lower than for the resistance minimum, then most of the energy is going into the ground wave Beverage mode. Thus, it is clear that the difference, for example, between a height of 0.02 and 0.05 produces a substantial change in the excitation efficiency of the dipole mode. For frequencies of4 MHz. to 6 MHz. over average or poor ground, such a height range difference may be between and feet. For the lower height, the reduction of efficiency due to resistance change alone may be 7 to 10 db. FIG. 4b is correlated to FIG. 4a and illustrates the power lost to the Beverage mode (in db) as a function of dipole height expressed in terms of operating frequency wavelength. Based on a minimum operating effectiveness, the effective antenna height for an operating frequency of 2 MHz. to 12 MHz. has been found to be about 12 feet with the dipoles being 15 feet and feet in length, respectively. While the present antenna is especially useful for sky wave radiation in adverse terrain, a desirable characteristic of the Beverage mode radiation, as above noted, is the availability of ground wave propagation, concurrently with the sky wave propagation, which enables direct communication over relatively short distances, e.g. up to 20 or miles depending on terrain.

Another embodiment of the antenna which utilizes rigid dipole elements and which is operable in either a horizontally polarized mode or a vertically polarized mode is shown in perspective in FIG. 5. The mast comprises a plurality of segments 42 similar to the mast segments for the antenna illustrated in FIG. I, and the mast is mounted on a base plate 44. Rigid radiating elements 46 and 48 form a long dipole, and radiating elements 50 and 52 form a short dipole. To facilitate impedance matching at various operating frequencies a balun wire 54 is provided on the mast which is connected to the center conductor of the coax feedline at the upper end of the mast and is switchably connected at its lower end to the outer conductor of the coax feedline (mast shell). Coax line 56 connects the mast feedline to radio 58 (such as the military AN/TRC-75 and the AN/TSCI5 radios). An A-frame lever 60 and a hand hoist 62 are utilized in erecting the antenna. The antenna can be erected by two men, as shown in flG. 6, in about 30 minutes. In erecting the antenna, the mast segments and dipole elements are assembled and the mast 40 is fastened to the base plate 44. Ground stakes or anchors 6d are driven into selected ground points and the guy ropes are attached to the anchors. By means of the A-frame lever 60 and the hand hoist 62, the mast is raised to an operating position. Final plumbing of the mast is accomplished by adjusting the guy ropes.

In a specific embodiment of the antenna designed for operation in the high frequency range, the mast 40 is 40 feet in height and each of the long dipole elements are 25 feet in length while each of the short dipole elements are l8 feet in length. The antenna weighs l9l pounds.

FIG. 7a and FIG. 7b are schematic representations of the antenna in a horizontal dipole mode of operation and in a toploaded vertical monopole mode of operation, respectively. In the horizontal dipole mode of operation illustrated in FIG. 7a, the dipole elements 70 are fed through the coaxial mast 72 which is connected to a transceiver (not shown) through dipole input connector 74. The mast 72 is supported on an insulating base plate 76 with the outer electrode of the coaxial mast 72 shorted to ground through monopole mode input connector 78. Balun wire 80 is shown shorted to the outer electrode of the coaxial mast 72 by means of switch 82. In a monopole mode of operation, the mast and dipole elements function as a top loaded vertical radiating element. As illustrated in FIG. 7b, when the antenna is used in this mode of operation, a shorting cap 86 is connected to the dipole mode input connector and all metal parts above the mast base 76 are connected electrically. In this configuration, the antenna becomes a vertical monopole with capacitive top loading, and is connected to the transceiver (not shown) through the coaxial connector 78. The 40 foot mast, loaded with its capacitive elements, has the electrical characteristics of a linear vertical element approximately 80 feet in height.

While the invention has been described with respect to specific embodiments, the description is illustrative and is not to be construed as limiting the scope of the invention. Various modifications and changes may occur to those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

We claim:

I. A portable radio antenna comprising a segmented mast which is easily assembled and disassembled, said mast including an outer metallic portion and an inner metallic portion which cooperatively function as a low-loss coaxial feedline, a plurality of horizontally polarizable radiating elements physically and electrically connected to a mast segment, said plurality of radiating elements angling downwardly from the top of said mast and functioning as guy wires and including a pair of dipoles with one dipole being longer than the other dipole, and input connector means for connecting said mast to a radio transceiver.

2. A portable radio antenna as defined by claim I and further including means for electrically shorting all electrically conductive portions of said antenna and a second input connector means for energizing said antenna as a top-loaded vertical antenna.

3. A transportable high frequency antenna comprising a segmented mast, each mast segment including an outer metallic portion and an inner metallic portion which is mechanically supported and axially aligned within and insulated from said outer portion and which cooperatively function as a low-loss coaxial line segment, a plurality of radiating elements mechanically and electrically connected to one mast segment, a balun wire electrically connected to the inner metallic portion of said mast and spaced in parallel axial alignment with said mast, switch means for electrically connecting said balun wire to the outer metallic portion of said mast, and means for connecting a radio transceiver to said mast.

4. A transportable high frequency antenna as defined by claim 3 and further including means for electrically shorting all electrically conductive portions of said antenna and a second input connector means for energizing said antenna as a top-loaded vertical antenna.

5. A transportable high frequency antenna as defined by claim 3 wherein said plurality of radiating elements are rigid.

6. A transportable high frequency antenna as defined by claim 3 wherein said plurality of radiating elements function as guy supports for said mast.

7. A manually transportable high frequency antenna which is easily assembled, disassembled and transported comprising a plurality of low-loss coaxial line segments which are assembled to form a support mast, each segment including an outer electrically conductive portion and an inner electrically conductive portion which is mechanically supported and axially erected mast, said plurality of radiating elements functioning as guy supports for said mast, and means for connecting a radio transceiver to the erected mast. 

1. A portable radio antenna comprising a segmented mast which is easily assembled and disassembled, sAid mast including an outer metallic portion and an inner metallic portion which cooperatively function as a low-loss coaxial feedline, a plurality of horizontally polarizable radiating elements physically and electrically connected to a mast segment, said plurality of radiating elements angling downwardly from the top of said mast and functioning as guy wires and including a pair of dipoles with one dipole being longer than the other dipole, and input connector means for connecting said mast to a radio transceiver.
 2. A portable radio antenna as defined by claim 1 and further including means for electrically shorting all electrically conductive portions of said antenna and a second input connector means for energizing said antenna as a top-loaded vertical antenna.
 3. A transportable high frequency antenna comprising a segmented mast, each mast segment including an outer metallic portion and an inner metallic portion which is mechanically supported and axially aligned within and insulated from said outer portion and which cooperatively function as a low-loss coaxial line segment, a plurality of radiating elements mechanically and electrically connected to one mast segment, a balun wire electrically connected to the inner metallic portion of said mast and spaced in parallel axial alignment with said mast, switch means for electrically connecting said balun wire to the outer metallic portion of said mast, and means for connecting a radio transceiver to said mast.
 4. A transportable high frequency antenna as defined by claim 3 and further including means for electrically shorting all electrically conductive portions of said antenna and a second input connector means for energizing said antenna as a top-loaded vertical antenna.
 5. A transportable high frequency antenna as defined by claim 3 wherein said plurality of radiating elements are rigid.
 6. A transportable high frequency antenna as defined by claim 3 wherein said plurality of radiating elements function as guy supports for said mast.
 7. A manually transportable high frequency antenna which is easily assembled, disassembled and transported comprising a plurality of low-loss coaxial line segments which are assembled to form a support mast, each segment including an outer electrically conductive portion and an inner electrically conductive portion which is mechanically supported and axially aligned within and insulated from said outer portion, a plurality of radiating elements mechanically and electrically connected to one segment which is positioned at the top of the erected mast, said plurality of radiating elements functioning as guy supports for said mast, and means for connecting a radio transceiver to the erected mast. 